It has long been recognized that firearms form an identifiable series of marks, or striations on a projectile as it is discharged from the firearm. Since the striations generally result from minor differences that ordinarily arise during the manufacture of the firearm, the striations are generally unique, so that detectable differences exist even for firearms contemporaneously produced by the same manufacturer. As a result, forensic ballistic investigations often use these unique striation patterns to establish an association between a recovered projectile, such as a bullet, and a firearm.
Various methods have been proposed that employ the striations formed on the projectile as the basis for an identification system for firearms. In one method, generally referred to as “ballistic fingerprinting”, a test cartridge is discharged from a firearm prior to the sale of the firearm. The components of the test cartridge are recovered and retained in a repository so that they may be accessed at some future time when ownership of the firearm must be established. Identifiable characteristics associated with the test cartridge components may include striation marks on a bullet, a firing pin mark on a cartridge casing, extractor marks on a rim of the casing, or other readily identifiable marks. Alternatively, the components of the test cartridge may be photographed or scanned to form an image record of the recovered components so that the image record may be stored in a data base. In either case, when the firearm is sold, the identity of the purchaser is associated with the information obtained from the test cartridge. When it becomes necessary to determine ownership of the firearm, for example, following the commission of a crime using the firearm, the recovery of the components of a cartridge discharged at the crime scene will permit the owner of the firearm to be identified by comparing the recovered components to the components retained in the repository, or alternatively, by comparing the recovered components to imagery stored in the data base.
Despite the obvious advantages afforded by ballistic fingerprinting methods, drawbacks nevertheless exist. For example, firearms manufactured and sold before the implementation of a ballistic fingerprinting program would not be identifiable through the program, since no test cartridge information would be present in a repository or a data base for these firearms. Accordingly, most of the firearms now in existence would remain non-traceable despite the implementation of the ballistic fingerprinting program. Further, even if test cartridge information exists for a firearm, certain methods used to manufacture components of the firearm may present difficulties when attempting to identify a firearm by ballistic fingerprinting. For example, in one present method, the barrel and receiver portion of the firearm is formed by shaping the barrel and receiver on a mandrel. The mandrel generally includes distinctive machining marks that are subsequently transferred to the barrel and receiver as they are formed. Accordingly, a large number of barrel and receiver portions formed on a common mandrel will generally include similar marks or striations that correspond to the marks present on the mandrel, thus reducing the presence of unique and readily identifiable patterns on the test cartridge. Additionally, components of the firearm may be selectively altered by reconfiguring the barrel and/or the receiver portion of the firearm so that it produces striations that differ significantly from the striation pattern that was obtained when the test cartridge was fired. Consequently, traceability of the firearm with reference to the test cartridge information could be easily defeated. Still further, the barrel and/or receiver portions of the firearm undergo various changes during normal use that may significantly affect the striations in the barrel, so that the fingerprint information associated with the firearm gradually changes over time.
Still other problems present exist with present ballistic fingerprinting methods. For example, components from different firearms may be exchanged, or may simply be replaced at some time during the life of the firearm as a part of a repair operation. In such cases, traceability is also lost since there is generally no requirement to document these operations in a ballistic fingerprinting program. Finally, the traceability of a firearm may also be lost by transferring ownership of the firearm to others through a series of undocumented personal transactions, so that the chain of ownership is lost.
An alternative approach is to position an identifying mark on a cartridge before the cartridge is sold, and to associate an identity corresponding to a purchaser with the identifying mark on a portion of a cartridge. Several significant advantages are evident in this approach. In general, no governmental agency would be required to supervise the test cartridge firing, and to retain the information in a central repository, or data base. Instead, ammunition having an identifying mark could be conveniently tracked through a chain of supply in a manner similar to ordinary inventory tracking, so that the costs associated with tracking the ownership of the marked ammunition are widely distributed. Furthermore, since the burden associated with identification of the firearm is effectively shifted from the firearm to the ammunition, the identity of a firearm owner or user may be determined without regard to the age of the firearm, so that all firearms currently in existence could be traced. Moreover, modification of the firearm by altering selected portions of the firearm would be ineffective in defeating an ammunition marking system. Still further, ammunition marking could not, in general, be defeated by undocumented firearms sales, since the documentation is associated with the ammunition rather than the firearm.
Various methods are present in the prior art for placing an identifying mark on ammunition. For example, U.S. Pat. No. 1,650,908 to Ramsey discloses an ammunition marking system that includes forming a single identifier on a rear face of a bullet. The single identifier, however, may be rendered unreadable by deformation of the bullet, thus defeating subsequent attempts to identify the bullet. Moreover, the single identifier is limited to the expression of relatively few numbers. Ramsey further discloses forming a single identifier on a rear surface of a cartridge by transferring an identifier present on a surface of a hammer of the firearm on to a rear surface of the cartridge. One particular shortcoming present in this approach is that it requires a suitably configured firearm.
Another prior art approach is described in U.S. Pat. No. 6,293,204 B1 to Regen, which discloses marking ammunition components with a binary code array. The array is a compact method for forming a binary number, so that many distinct numbers may be expressed. Although the binary arrays disclosed by Regen allow the formation of more distinct numbers than permitted by Ramsey, the method still relies on the formation of a single number on the ammunition component. Consequently, if various bits within the binary array are rendered unreadable by deformation of the bullet, or by other means, subsequent identification of the ammunition component may not be possible. In addition, the binary array may not be deciphered by persons not having specialized training directed to reading the contents of the binary array. Accordingly, the ability of law enforcement agencies to read the contents of the array and to readily identify the ammunition component is impeded.
What is required in the art is a marking method that allows an identifying mark to be repetitively formed on an article of ammunition so that at least one of the marks remains identifiable despite the deformation or even partial destruction of the ammunition components.